Adhesions are fibrous bands of tissue connecting one or more organ sites within the body. More specifically, adhesions as concerned here occur as a result of post-surgical tissues growing together either between layers of adjacent bodily tissue or between tissues and internal organs. Adhesions can form during the healing which follows surgical procedures, and when present, adhesions can prevent the normal motions of those tissues and organs with respect to their neighboring structures.
Although the inventor does not wish to be bound by any particular theory of the invention, it is believed that the adhesions occur when the tissue becomes injured. Typically injury to, or ischemia of, serosal tissue results in an increased immune response at the site, with a subsequent release of serosanguinous exudate resulting in fibrin deposition at the injured site. Adhesions form as a result of the induced inflammatory response in combination with an impaired ability to lyse such fibrin deposits. Generally, in normal tissues the tissue surface produces tissue plasminogin activators (t-PA) which converts inactive plasminogen to plasmin. This protolytic mechanism of plasmin dissolves fibrin deposits and thus prevents adhesion formation. However, ischemic injury to serosal surfaces retards t-PA production. Reduced t-PA production results in excessive fibrin accumulation at the injured site. Such fibrin deposits serve as a matrix for fibroblastic infiltration and proliferation. Eventually, collegenous bands contract as healing proceeds and thereby limit movement of the affected organ or organs.
Consequently, adhesion formation results generally from thoracic, abdominal, lumbar and/or gynecological surgeries and represents a significant clinical problem across many different fields of medicine. Postoperative adhesions occur in 70-95% of all cases. For example, post-surgical peritoneal adhesions are one of the leading causes of intestinal blockage or obstruction (Ellis, Surg. Gynecol. Obstet. 133:497, 1971), and are also of great concern to surgeons who attempt to improve fertility in women through reconstruction. Pelvic adhesions can impair fertility by interfering with the ability of the fallopian tubes to pick up the ovum (Holtz, Fertil. Steril. 41:497, 1984; Diamond and Hershlag, Prg. Clin. Biol. Res. 358:23, 1990). The formation of permanent adhesions in tendons and joints is a major cause of decreased mobility and chronic pain.
Over the years many different strategies have been employed to prevent the formation of adhesions. Good operating techniques, gentle handling of tissues, lavage of the peritoneal cavity, hemostasis, and irrigation will prevent the formation of adhesions to a certain extent, however, these procedures never completely inhibit adhesion formation after surgery. Therefore, numerous approaches to elimination of adhesion formation have been attempted, with limited success in most cases. Approaches have included the mechanical separation of tissues or the administration of pharmacological agents.
A mechanical separation or barrier material, is typically applied as a sheet or film and sutured in place to prevent the deposition of fibrin. Examples of such materials include oxidized cellulose membranes, polytetrafluoroethylene, or hyaluronic acid. However, most such barrier materials have proven unsuccessful. For example, Interceed.TM. Barrier, and oxidized cellulose is very difficult to place and can only be applied to a non-bleeding site. Gore-Tex.TM., poses another problem by having to always be sutured in place and must eventually be removed. This removal process further introduces additional potential trauma or injury to the tissue. Seprafilm.TM., a hydaluronic acid film, becomes very brittle and has a tendency to crack. This tendency results in an inadequate barrier between the injured tissue and the surrounding tissue, which in turn increases the chances of adhesion formations.
Another approach used to prevent the formation of adhesions is the use of pharmaceutical agents. Typical pharmaceutical agents include corticosteroids and nonsteroidal anti-inflammatory agents (to inhibit fibroblastic proliferation); heparin and sodium citrate (to prevent fibrin deposition); and pentoxifyline, rt-PA, urokinase and streptokinase (to promote fibrinolysis). Unfortunately, the success of pharmaceutical agents in preventing adhesion formation has been limited, due to the difficulty of directing the drugs to the injury with systemic administration.
In summary, several approaches have been explored, but none have been able to achieve the desired system, which is successful in preventing adhesion formation after surgery, can be applied easily to the surgical site and still be effective. Additionally, the ability of an anti-adhesion composition that remains intact at the surgical site during the initial stages of critical wound healing is also desirable. Moreover, a system that allows for local administration of a composition, which prevent adhesion formation would be most desirable.